Establishing a Lesser Kestrel Colony in an Urban Environment for Research Purposes

Abstract

ESTABLECIMIENTO DE UNA COLONIA DE CERNÍCALO PRIMILLA FALCO NAUMANNI EN UN AMBIENTE URBANO CON PROPÓSITOS DE INVESTIGACIÓN Debido al declive reciente de las poblaciones de Falco naumanni, se han llevado a cabo numerosos proyectos de reintroducción y refuerzo de sus poblaciones en varios países mediterráneos. Aprovechando la experiencia de proyectos previos, intentamos establecer una colonia de F. naumanni en la cubierta de la sede central de la Estación Biológica de Doñana, un edificio moderno y recientemente construido en Sevilla, sur de España. Nuestro objetivo es obtener un acceso fácil a una población urbana y silvestre de esta especie modelo con fines científicos. Después de la liberación de los primeros individuos mediante el método de crianza campestre hace cinco años, nuestra colonia experimental parece haberse establecido. Tres, seis y tres parejas intentaron reproducirse en los años 2010, 2011 y 2012, respectivamente.

Full text

SHORT COMMUNICATION
J. Raptor Res. 47(2):214–218
E2013 The Raptor Research Foundation, Inc.
ESTABLISHING A LESSER KESTREL COLONY IN AN URBAN ENVIRONMENT FOR RESEARCH PURPOSES
AIRAM RODRI
´GUEZ AND JUAN J. NEGRO
1
Department of Evolutionary Ecology, Estacio´n Biolo´gica de Don˜ana, CSIC, Avda. Ame´rico Vespucio s/n, 41092 Seville, Spain
JAVIER BUSTAMANTE
Department of Wetland Ecology, Estacio´n Biolo´gica de Don˜ana, CSIC, Avda. Ame´rico Vespucio s/n, 41092 Seville, Spain
JOSE
´ANTOLI
´N
DEMA, Defensa y Estudio del Medio Ambiente, Ctra. Fuente del Maestre, km 17,
06200 Almendralejo, Spain
KEY WORDS:Lesser Kestrel; Falco naumanni; captive breed-
ing;hacking ;reinforcement ;reintroduction.
Raptors are top predators sensitive to changes and per-
turbations in the food chain, and as a consequence, they
function as good bioindicators for environmental and eco-
system health. Captive breeding facilities have been creat-
ed at research centers or universities to study biological
traits of several raptor species (e.g., the American Kestrel
(Falco sparverius) has been used as a wildlife study model
for over four decades, probably becoming one of the most
studied raptors in the world; Bardo and Bird 2009).
Among wild populations, the Lesser Kestrel (Falco nau-
manni) is one of the most studied raptors in Europe, espe-
cially in the Mediterranean Basin. It is a study model
species for a variety of biological disciplines: genetics, phys-
iology, migration, behavioral ecology, population ecology,
and conservation biology in a broad sense. The goal of this
report is to describe the development of a project to estab-
lish an artificial Lesser Kestrel colony on the roof of a
biological research center located within an urban area
(Seville, southern Spain). This colony provides many of
the logistic advantages of a captive breeding facility, but
uses wild birds; and consequently, will be useful for studies
of the species’ biology and ecology. In addition, our colony
will help conserve the species in an urban environment by
providing predator-free nest-sites and reinforcing a deci-
mated population.
METHODS
Study Species. The Lesser Kestrel is one of the smallest
European raptors (wingspan 58–72 cm, body mass 120–
140 g). Breeding range of this migratory falcon extends
from China to the Iberian Peninsula and its wintering
grounds are located in sub-Saharan Africa. It breeds in
small colonies numbering 1 to 100 breeding pairs. Lesser
Kestrels nest in holes and crevices available on natural
cliffs, but also in buildings such as castles, churches, and
old buildings, especially in its western breeding range. It is
linked to steppes and pseudo-steppes (cereal fields and
pasturelands), where it obtains its primary prey, arthro-
pods (i.e., grasshoppers, beetles, crickets; see Negro 1997
for more information on the species).
The Lesser Kestrel suffered a severe decline during the
second half of the 20
th
century probably due to habitat loss
and degradation as a result of agriculture intensification.
However, as the population has been stable for the last two
decades, it has been downlisted from Vulnerable to Least
Concern according to IUCN criteria (BirdLife Internation-
al 2011). Because of the decline of the Lesser Kestrel,
numerous conservation programs involving captive breed-
ing for reintroduction and reinforcement purposes (Po-
marol 1993, Alcaide et al. 2010), rehabilitation of nests
and colonies (Pomarol 1996, Bux et al. 2008, Catry et al.
2009, Pe´ rez et al. 2011), and enhancement of foraging
habitats have been put in place.
Creating a New Lesser Kestrel Colony. The physical
structure for the colony consisted of two elongated brick
constructions on the roof of a five-floor building, at the
headquarters of Don˜ana Biological Station, at a height of
28 m above the street level (Fig. 1). Although the building
is located within the urban area of the Isla de La Cartuja,
Seville, southern Spain, it is on the northernmost edge of
the city facing agricultural fields. Cereal fields extend to-
ward the northwest, the nearest ones ,500 m away from
the office building and thus the colony. This area is inten-
sively cultivated, with small plots of cereal, sunflower, olive
groves, and other minor crops. Forty wooden nest boxes
with easy access (for capture of birds at the nests from
inside the building) were mounted on the north wall
(Fig. 1). Nest-box dimensions were 40 330 325 cm.
1
Email address: negro@ebd.csic.es
214

The size of the entrance was 7.5 cm in width and the cor-
ridor to enter the nest-box breeding chamber was 15 cm
long to exclude feral pigeons (Columba livia) and jackdaws
(Corvus monedula), potential competitors for nest-holes
(Forero et al. 1996). Sand was added to the nest boxes to
provide a soft substrate and minimize egg-rolling. In Seville
city, to our knowledge the largest city in western Europe
with Lesser Kestrel colonies, at least three urban colonies
contain a total of about 100 pairs (Negro et al. 2000).
Hacking Program. Nestlings. In 2008, a hacking pro-
gram was started by releasing nestlings 18- to 24-d old from
a captive breeding program (Lesser Kestrel Breeding Cen-
ter of DEMA, Almendralejo, Spain, www.demaprimilla.
org). Nestlings were banded with metal and plastic bands,
and released into the hacking nest boxes. Food (white
mice) was cut up into pieces of different size according
to nestling age and provided ad libitum.
Conspecific attraction. In addition, captive adult Lesser
Kestrels (1–4 birds per year) were maintained during four
breeding seasons (2008–11) from late February to late July
in an external wire netting cage (6 3232 m). These
kestrels were permanently injured and could not be reha-
bilitated to be released to the wild. They were provided by
DEMA from their captive stock. The purpose of keeping
captive birds was twofold. First, Lesser Kestrel colonies
seem to grow due to conspecific attraction (Serrano and
Tella 2003, Serrano et al. 2003, 2004), and therefore, they
might attract conspecifics to the colony after their pre-
breeding migration, both free-living and hacked birds. Sec-
ond, the cage of adults was situated in the front portion of
the colony and it was adjacent to the nestlings’ hacking
nest boxes, separated from them only by a wire mesh
through which the adults could feed the nestlings. Thus,
when adults were fed, nestlings begged for food and cap-
tive adult birds acted as foster parents feeding the nestlings
(see Antolı´n 2001).
Supplementary feeding. During the 2008–12 breeding sea-
sons we provided supplemental food to the colony. We
Figure 1. Lesser Kestrel breeding colony located at the headquarters of Don˜ ana Biological Station (Seville, Spain). (A)
Inside view (Photo: Airam Rodrı´guez). (B) Nestlings in a nest box used by wild Lesser Kestrels (Photo: Airam Rodrı´guez).
(C) Female Lesser Kestrel hacked and resighted at the colony (Photo: Jose´ Antolı´n/DEMA). (D) Headquarters of
Don˜ana Biological Station in Seville with the Lesser Kestrel colony located at the roof (Photo: Jose´ Antolı´n/DEMA).
(E) Cage with adult birds inside and hacked fledglings resting outside (Photo: Jose´ Antolı´n/DEMA).
JUNE 2013 SHORT COMMUNICATION 215

used dead 3-d-old chicken chicks and white mice provided
by a commercial supplier. Food was left on the captive
kestrels’ cage and in the vicinity of the artificial colony.
The amount of food provided depended on the number
of birds and phase of the breeding season.
RESULTS AND DISCUSSION
A total of 149 captive-hatched nestlings were released
from 2008 to 2010 (Table 1). One and ten wild-reared
nestlings fallen from their nests and admitted to the
DEMA facilities in 2008 and 2009, respectively, were addi-
tionally released in the hacking program. In 2009, captive
birds kept in the central cage raised two additional fledg-
lings that were eventually released by hacking.
Twenty-three of the 162 nestlings of different origins
released by hacking (14%) were observed at the colony
during the years post-release (Fig. 2). Eight of the 23 birds
sighted have tried to breed at least once (5% of released
birds). Furthermore, one fledgling released by hacking
from our colony in 2010 was recaptured as a breeder in
2011 and 2012 at a colony 48 km away, and at least one
other fledgling was sighted as a breeder at another nearby
colony (,1 km away) that was not used by Lesser Kestrels
when the program started. The return and recruitment
rates observed in the following years at our colony were
lower than or similar to those reported for other reintro-
duction programs carried out in Catalonia (25% of hacked
birds were resighted and 17% recruited as breeders; Po-
marol et al. 2001, 2009) or in Valencia (12.5% of hacked
birds were resighted; M. Romero pers. comm.). However,
in Catalonia, rates were calculated taking into consider-
ation the sightings and recruitments at nearby colonies
(buildings), whereas we only routinely monitored the one
colony on our roof. It is known that conspecific attraction
plays animportant role in the settlement of Lesser Kestrels
(Serrano and Tella 2003, Serrano et al. 2003, 2004);
therefore, the probability of natal dispersal to another
colony, i.e., the probability of breeding at a colony other
than the natal colony, decreases with the size of the natal
colony and with the distance to the nearest colony (Ser-
rano et al. 2003). Therefore, hacked birds from our
building may be recruiting to other larger neighboring
colonies in Seville.
Breeding pairs were established in the second year of
the release project (Table 1). The first breeding pair was
Table 1. Number of individuals sighted and breeding rates of the Lesser Kestrel (Falco naumanni) at the breeding
colony in Don˜ana Biological Station, Seville, Spain.
YEAR
2008 2009 2010 2011 2012 TOTAL
No. of fledglings released (hacking) 51 58 40 - - 149
No. of birds resighted
1
0 10(1) 16(6) 16(8) 10(6) 35(12)
No. of pairs established 0 1 3 6 3 13
No. of eggs laid - 0 20
2
26
3
12 58
No. of chicks fledged - - 5 6 9 20
Mean clutch size
4
- - 5 4 4 4.25
Breeding success (fledglings per
successful pair)
- - 2.5 3 3 2.86
Breeding success (fledglings per
breeding attempt)
- - 1.67 1 3 1.54
1
No. of birds resighted 5Adult birds individually identified by PVC bands. In parentheses is the number of adult birds originating from
other colonies.
2
One pair laid ten eggs in four different nest boxes.
3
Two pairs laid four and six eggs in four and four different nest boxes, respectively.
4
Excluding abnormal clutches (i.e., those clutches coming from pairs laying eggs in different nest boxes).
Figure 2. Number of hacked fledglings resighted at the
colony during subsequent years. * Open bar for 2010 in-
dicates fledglings produced by breeding pairs established
at the colony (i.e., they were not released by hacking).
216 SHORT COMMUNICATION VOL. 47, NO.2

formed by yearlings (one female released the previous year
and a first-year-plumage wild male). The age of this pair
corresponds well with the information reported from other
sites, i.e., high frequency of yearlings and first-time breeders
in small colonies (Serrano and Tella 2007). Six of the 13
individually identified breeders involved in the 13 breeding
attempts were hacked as fledglings at our colony. There-
fore, at least 54% of the breeder birds were of wild origin
and were attracted from elsewhere (note that two birds were
not captured and banded when they attempted to breed,
and thus, this percentage may be higher). The majority of
Lesser Kestrels in Europe breed in old buildings with a high
availability of holes due to their poor condition or poor
maintenance. However, if these old buildings are finally
repaired or restored, holes are usually eliminated, limiting
the availability of nest sites (although this practice is cur-
rently changing thanks to conservation guidelines; de la
Riva and Serrano 2004). Therefore, the provision of 40 nest
boxes in our colony has increased nesting sites for the spe-
cies, assisting in its conservation as indicated by the fact that
immigrants from other colonies have been able to breed at
our building (but see Pe´rez et al. 2011). Our colony located
on the roof represents safe (free from predators) and long-
lasting nesting sites for Lesser Kestrels (Franco et al. 2005).
In a similar way, the Lesser Kestrel population in Portugal
has benefited by the provision of nest boxes, and currently
52% of that country’s population breeds in artificial nest
cavities (Catry et al. 2009).
Rural colonies of Lesser Kestrels tend to have higher
breeding and prey delivery rates than urban colonies (Tella
et al. 1996, Negro et al. 2000). However, the breeding suc-
cess of our colony ranged between 2.5–3 fledglings per suc-
cessful pair, higher rates than those reported in nearby rural
colonies (e.g., Rodrı´guez et al. 2006). The high breeding
success may be related to the supplementary feeding. All
breeders at our colony were observed eating supplemented
food at least once (birds released by hacking were observed
using supplemented food more frequently than wild birds),
as well as some Lesser Kestrels from other colonies and at
least two female Eurasian Kestrels (Falco tinnunculus). The
provision of safe nest sites and supplemental food has ben-
efited not only Lesser Kestrels (Pomarol 1996, Bux et al.
2008, Catry et al. 2009), but also other kestrel species, such
as the endangered Mauritius Kestrel (F. punctatus). Supple-
mentary feeding allowed Mauritius Kestrel pairs to raise
larger broods, and nest boxes increased the numbers of
breeding kestrels by providing nest sites in areas previously
lacking them (Jones 2004).
Despite the recent implementation of the project (only
5 yr ago) and the small number of pairs breeding at the
colony, it is already yielding scientific outputs. Two different
projects have been carried out using the colony as a model.
In one study, we have combined the use of GPS data-logger
information obtained from free-ranging birds, and environ-
mental information recorded by unmanned aerial systems
(UASs) to study foraging habitat selection of breeders,dem-
onstrating that UASs can obtain environmental information
at quasi-real time for wildlife studies (Rodrı´guez et al. 2012).
In another study, we have measured the metabolic costs of
the immune response of hacked and wild-reared nestlings.
As a caveat, we note the small size of the colony so far makes
it possible that the colony might yet fail.
Conclusions. Urban bird species have an environmental,
cultural, touristic, and even educational value, and play a
key role for enhancing environmental awareness among
city dwellers. They should not be neglected or overlooked
in a modern world where urban areas increase along with
the proportion of the human population inhabiting them.
In the case of the Lesser Kestrel, it has been predicted that
the western European population will soon depend on
artificial nest sites (Catry et al. 2009). Modern architecture,
often heralded as eco-friendly, should not only target eco-
nomic, energetic, and functional optimization, but also
consider providing suitable nesting habitat for important,
native urban species.
ESTABLECIMIENTO DE UNA COLONIA DE CERNI
´-
CALO PRIMILLA FALCO NAUMANNI EN UN AMBIENTE
URBANO CON PROPO
´SITOS DE INVESTIGACIO
´N
RESUMEN.—Debido al declive reciente de las poblaciones de
cernı´calo primilla Falco naumanni, se han llevado a cabo
numerosos proyectos de reintroduccio´n y refuerzo de sus
poblaciones en varios paı´ses mediterra´neos. Aprovechando
la experiencia de proyectos previos, intentamos establecer
una colonia de F. naumanni en la cubierta de la sede central
de la Estacio´n Biolo´ gica de Don˜ana, un edificio moderno y
recientemente construido en Sevilla, sur de Espan˜a. Nues-
tro objetivo es obtener un acceso fa´cil a una poblacio´ n ur-
bana y silvestre de esta especie modelo con fines cientı´ficos.
Despue´s de la liberacio´ n de los primeros individuos med-
iante el me´todo de crianza campestre hace cinco an˜os, nues-
tra colonia experimental parece haberse establecido. Tres,
seis y tres parejas intentaron reproducirse en los an˜ os 2010,
2011 y 2012, respectivamente.
[Traduccio´ n de los autores editada]
ACKNOWLEDGMENTS
We are grateful to the volunteers involved in the breed-
ing program at DEMA. Antonio Rivera helped us during
the hacking activities. Carlos Rodrı´guez, Tom J. Cade,
Vicente Urios, Cheryl Dykstra, and an anonymous reviewer
provided valuable comments on early versions of this man-
uscript. This project complies with Spanish and European
legislation. Junta de Andalucı´a issued the necessary per-
mits to carry out the hacking process. This paper is dedi-
cated to the memory of our friend and colleague - the late
Gary R. Bortolotti.
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